Authorities in France have blocked trains from Italy in an attempt to stop north African migrants from entering the country.Trains carrying migrants and political activists have been stopped at the border - prompting Italy to launch an official complaint with its neighbour.
Italy has angered France by giving out temporary resident permits to thousands of Tunisian migrants.
The permits allow them to travel freely in many European countries.
The Italian foreign ministry said the French move was "illegitimate and in clear violation of general European principles".
Schengen infringement?
Maurizio Furia, a spokesman for the Italian rail company, said that trains were not being allowed to pass into Menton, France, from the Italian border station of Ventimiglia.
France says migrants have to prove they can support themselves financially and has set up patrols on the Italian border.
But Italy says that France's actions are in violation of the EU's Schengen passport-free travel zone.
"We have given the migrants travel documents, and we gave everything (else) that is needed, and the European Commission recognised that, it has said that Italy is following the Schengen rules," Italian Interior Minister Roberto Maroni said in an interview on Italy's Sky TG24 TV.
Italy and other European countries have been increasingly concerned about migration from north Africa following the political turmoil in the region.
Earlier this month, Italy and France agreed to launch sea and air patrols to try to prevent the influx of thousands of people from Tunisia, Egypt and Libya.
